1. Field of the Invention
The present invention relates generally to a wireless power transmission and reception system, and more particularly, to a method and apparatus for controlling power of a receiver in a wireless power transmission and reception system, wherein a wireless power quantity supplied to receivers from a transmitter is controlled through communication between the receivers.
2. Description of the Related Art
Wireless charging (or non-contact) technology uses wireless power transmission and reception, for example, to charge a battery of an electronic device by placing the electronic device on a charging pad, without having to connect a separate charging connector to the electronic device.
Wireless charging technology may be roughly divided into an electromagnetic induction type using a coil, a resonance type using resonance, and a Radio Frequency (RF)/micro wave radiation type for transforming electrical energy into a microwave.
In the resonance type of the wireless charging technology, a resonance type power transmission principle is used to wirelessly transmit electricity a distance of several meters from a charging device. Basically, resonance type power transmission uses a similar concept of physics in which vibration of a tuning fork causes a wine glass beside the tuning fork to vibrate at the same frequency. However, instead of resonating sound, resonance type power transmission resonates an electromagnetic wave containing electrical energy.
The resonated electrical energy is directly delivered to a device having a same resonance frequency, and the non-used portion of the resonated electrical energy is absorbed again into an electromagnetic field, instead of being spread through the air, such that unlike other electromagnetic waves, the resonated electrical energy does not to have an influence upon a peripheral machine or human body.
When charging using the resonance type of the wireless charging technology, each of a plurality of receivers that wants charging requests transmission of wireless power from a transmitter for transmitting the wireless power. The transmitter then supplies wireless power to each of the receivers. Basically, the receiver requests the transmitter to transmit wireless power, and is supplied with wireless power from the transmitter in response to the request.
Additionally, a single transmitter may charge a plurality of receivers at the same time. Further, when a receiver is being charged, i.e., supplied with wireless power from the transmitter, the transmitter may receive a request to transmit wireless power from another receiver.
However, when a plurality of receivers are supplied with wireless power from a transmitter at the same time, an over-powered state of over-voltage or over-current may occur in the transmitter or the receivers. Thereafter, the transmitter or receivers stop the charging, for example, by short-circuiting a circuit or the like, to protect against over powering. However, when the transmitter or the receivers stop the charging in this way, inconveniently, a user cannot charge the receiver using the transmitter or cannot use the receiver.